Assessment of nasal marker materials and designs used on dabbling ducks

Abstract

Four examples illustrate the relative performance of the shortcut estimator (Table 1). If the maximum-likelihood estimate provides the standard against which the others are judged, we see that the shortcut method provides similar values, but not quite as close as the Mayfield estimator. The apparent rate of nest success is the most severely biased. We recommend that the maximum-likelihood or Mayfield method be used whenever feasible (see Klett and Johnson [1982] for other suggestions and Bart and Robson [1982] for sample size considerations). The apparent rate of nest success should be avoided except under unusual circumstances in which successful and unsuccessful nests are equally likely to be found. The shortcut method proposed here is a useful approximation for quick and dirty analyses, when detailed data on all nests are not available, or as a check on the calculation of Mayfield estimates. Only the age of each nest when found and its ultimate fate are needed to calculate this new estimator. Acknowledgments.-We appreciate comments on an earlier draft of this article by J. Bart, H. F. Duebbert, H. F. Mayfield, H. W. Miller, and T. L. Shaffer.